Weeds to eliminate!

Pest Plants

Also known as noxious weeds.

More information on the Pest plants flyer.

They are a concern to Forest and Bird as they are a major threat to the Waitakare Ranges Heritage Area which was established to protect and maintain native flora and fauna.
Pest plants also threaten our local bush and gardens. Some of them are food for NZ’s native birds but our native trees need our native birds to prosper and pest plants are diverting them!
There are several excellent national web sites to help you deal with your pest plants but here we also add a local perspective.

As many of these pests do not compost but just keep growing try www.weedfree.org.nz for the location of the weed bin nearest to you. In March they are sited throughout our area but there are some permanent ones.
Containers for drowning ginger, Weed Containment bags, or War on weeds bags are available from the Weedfree Trust at various prices, phone 826 4276

Please do not tip any pest plants anywhere!

When the pests are dead consider replanting with natives, as weeds love a vacuum and will soon take advantage of fallow ground.


Ginger

Two species, Kahili ginger, Hedychium gardnerianum and Yellow ginger, Hedychium flavescens, are pests. They may be beautiful but would be better eliminated.

The problem
Ginger smothers native plants. It smothers any plants. It takes over in sun or shade. The roots, or more correctly rhizomes, spread into deep beds. It you break a piece off, it will grow, if you throw it away, it will grow. The birds feast on its sticky berries and spread the seed through their droppings, far and wide.

The solution
If possible root it out, otherwise, as a temporary measure, cut it back. The tops make good compost but the fruits and roots do not compost, they just keep growing. One way to dispose of them is to drown them, also known as neutralizing them. Pack them into a container, cover with water, and leave them there for a few of months. Alternatively cut them back then spray them. That is the end of them………until a bird brings some more from a weedy property.

Replant
If you have removed your ginger from a bush section replanting may not be necessary, small native plants quickly reestablish, regaining the land that should always have been theirs! However if this leaves a gap on a bank or other open area you may want to consider some of the many native plants that grow in the Auckland Region. These include low growing Parataniwha for damp shady areas and Rengarenga for drier places, but your choice is much wider, from Meadow Rice Grass/Paatiitii to a small tree such as wineberry, Aristotelia serrata.


Wandering Willie/Wandering Jew, Tradescantia fluminensis

The problem
The accompanying photo shows wandering willie in the process of smothering Asplenium oblongifolium, a familiar fern widespread in our area. Wandering willie, introduced as a garden plant from South America, moves with ease from our sections to the forest. Where it becomes established it overwhelms what is already growing there and prevents native seeds and seedlings from establishing.

There is GOOD NEWS. The Tradescantia leaf beetle, a Brazilian insect, after years of testing, was released into the NZ environment in 2011. It feeds on the foliage of wandering willie and no other plant. Another three insects are also being investigated as biocontrols for this pest plant. Until these very welcome beetles munch their way to the Waitakeres wandering willie will continue to overwhelm native forest plants.
http://www.landcareresearch.co.nz/news/release.asp?Ne_ID=304

The solution
Visit your wandering willie patch with a large sheet of plastic or something similar. Don your gloves first as some people (and dogs) suffer a skin reaction from this pest. Roll the plant onto the plastic, roll up the sheet, load it into your car boot and take it to a weed bin. This greatly reduces the chance of spillage and a new patch of wandering willie establishing. Even tiny segments of this pest plant can grow and overwhelm more desirable plants. Alternatively purchase a weed containment bag from the Weedfree Trust.
If you have them, hens will clear up the remains of the wandering willie. Alternatively you can now sit down and start picking up the remaining fragments and placing them in a secure container to transport them to the weed bins.

Another option is to spray using a fixative to penetrate those shiny leaves. But before spraying look for evidence of those Tradescantia leaf beetles (Neolema ogoblini) as you do not want to harm them!

Replant
There are many choices available to replant in your vacated wandering willie site. Ground covers, Fushia procumbens and pratias, thrive in the partial sun/shade areas that that pest lives in, small sized, small leafed Coprosmas and Muehlenbeckias have delightful textures (and attract birds) and small trees such as Rangiora, and Olearias may suit. Check with a native plant specialist nursery or try www.oratianatives.co.nz to see which plants would do best in your particular situation


Moth Plant Araujia hortorum, (previously Araujia sericifera)

The problem
Flowering in March and producing seed pods into winter, each containing up to 500 seeds, it is one of the worst, a pest plant. Moth plant is also known as kapok plant, Introduced to our country from South America as a garden plant the wind disperses its seed across the city. The masses of seeds establish in sun or shade, whether it be damp or dry or even salty. The vine grows quickly, produces flowers in its second year, climbs over, shades, then smothers any other plants as it develops into a large, heavy, long lived pest.

The solution
We urge you to don your gloves (its milky sap may irritate your skin), and eradicate it! Pull out seedlings if you recognize them but if the plant is any larger it may be necessary to cut it and smear the cut stump with some poison, such as vigilant, to kill it, as stumps can resprout. Moth plant is listed as a containment plant in this area which means if it is growing on your property you should eradicate it. The seeds and pods of this pest will not compost, they will grow! If your moth plant is hosting monarch butterfly caterpillars in summer please pick off the flowers and pods. Kill the vine late autumn and replace it with other caterpillar food plants for next summer.

Replant
There are some beautiful native flowering vines to replace this pest with if you need a vine; clematis, parsonsia, and tecomanthe, should be available at any good plant shop.


Plectranthus, blue spur flower.

Plectranthus ciliatus is an attractive looking plant which is included in the National Pest Plant Accord. It is sometimes known as blue spur flower. It was introduced to New Zealand from eastern South Africa and sold as a trailing pot plant. It first became established in the wild in 1965. Waitakere Forest and Bird is aware that it is still grown as a garden plant but suggests it be removed.

The problem
Plectranthus enjoys the damp soil and shade of the forest of the Waitakere Ranges Heritage Area and spreads with straggling but vigorous runners under the canopy, hedges and streams soon forming thick mats that smother small plants and suppress seedling growth. Definitely not attractive behavior!

The Solution
Plectranthus is one of the easier pest plants to control. It can be physically picked up or raked up, and all parts of it will compost in the compost bin, or else it can be buried. Some root fragments may recover, regrow, and be removed later. Alternatively cover the ground with a weed mat for about six months. Do watch your compost, however, as mentioned, this plant does spread by straggling runners and if they escape they will grow. Many areas of plectranthus have established from discarded garden waste. A spray such as Roundup will kill the plant.

Replant
Plectranthus will have been smothering many little native seedlings but with its removal some of the seeds may still be viable and they may grow. NZ has beautiful native ground covers but they do not all survive in the variety of light and moisture conditions that plectranthus does. You may want to consult “100 best NZ Native Plants for Gardens” by Fiona Eadie as she illustrates 16 ground covers and has reference to more.

 

 Plectranthus is in the Surveillance pest plant category. This does not mean we just watch it grow! Surveillance pests may no be sold, propagated or distributed and the public are encouraged to remove them from their property. There are no quick fixes for pest plants, thus Forest and Bird welcomes your participation in the road to eradication of these unwanted invaders! For pest plants growing on Council land or road reserve please phone 3010101 to report them.